Involvement of cytochrome c oxidase subunits Va and Vb in the regulation of cancer cell metabolism by Bcl-2

Abstract

Bcl-2 has been shown to promote survival of cancer cells by maintaining a slight pro-oxidant state through elevated mitochondrial respiration during basal conditions. On oxidative stress, Bcl-2 moderates mitochondrial respiration through cytochrome c oxidase (COX) activity to prevent an excessive buildup of reactive oxygen species (ROS) by-production from electron transport activities. However, the underlying molecular mechanism(s) of Bcl-2-mediated ROS regulation and its impact on carcinogenesis remain unclear. In this study, we show that Bcl-2 expression positively influences the targeting of nuclearencoded COX Va and Vb to the mitochondria of cancer cells. In addition, evidence is presented in support of a protein-protein interaction between COX Va and Bcl-2, involving the BH2 domain of Bcl-2. Interestingly, episodes of serum withdrawal, glucose deprivation or hypoxia aimed at inducing early oxidative stress triggered Bcl-2-overexpressing cells to preserve mitochondrial levels of COX Va while depressing COX Vb, whereas the reverse was observed in mock-transfected cells. The unique manner in which Bcl-2 adjusted COX subunits during these physiological stress triggers had a profound impact on the resultant decrease in COX activity and maintenance of mitochondrial ROS levels, thus delineating a novel mechanism for the homeostatic role of Bcl-2 in the redox biology and metabolism of cancer cells.

Loss of IL-15 receptor α alters the endurance, fatigability, and metabolic characteristics of mouse fast skeletal muscles

“…At the protein level, muscles from IL-15Rα-KO mice contained more PPARδ as well as cytochrome c oxidase (COX) subunit Va, the subunit responsible for partially regulating the activity of the COX unit (ref. 36 and Figure 5, D and E). These data confirm the alteration in mitochondria, ascertained by SDH fiber quantification in EDL muscles from IL-15Rα-KO mice.…”

The small GTPase Rac1 is a novel binding partner of Bcl-2 and stabilizes its antiapoptotic activity

“…Subcellular fractions were obtained as previously. 17 The immunocomplexes were analyzed by Western blotting as previously 18,19 and probed with anti-Rac1 (Upstate Biotechnology), anti-pan Ras, anti-Bax, anti-Bcl-xL, or anti-Bcl-2 (Santa Cruz Biotechnology). For GSTpulldown assays, GST-Rac1 (10 g) was incubated with 40 L glutathione Sepharose-4B beads (30°C; 1 hour) followed by incubation with recombinant proteins or cell extracts (4°C; overnight).…”

Identification of NCF2/p67phox as a novel p53 target gene

“…[14][15][16][17][18] The upregulation of Nox is critical to support the elevated glycolysis by providing additional NAD+, and it has been consistently observed in cancer cells and in primary pancreatic cancer tissues with compromised mitochondria. 9,19 In addition, in acute leukemic cell lines, Nox2-and/or Nox4-derived ROS are crucially involved in the modulation of glucose transport (mediated by Glut1), which is frequently upregulated controlled, a task which is performed by two interconnected systems: thioredoxin and glutathione system. [37][38][39][40][41] Interestingly, p53 and its family members positively regulate expression of genes whose products are directly involved in both systems; therefore, p53 clearly acts in an anti-apoptotic manner.…”